Featured Story – Making an entrance… stainless steel dazzles in Tokyo

Tokyu Plaza Making an entrance...
Stainless steel dazzles in Tokyo

Text & images by Kikukawa

Tokyu Plaza Omotesando Harajuku, owen by Tokyu Corp., is located in one of the most fashionforward areas of the city, at the intersection of Omotesando and Harajuku streets. A stunning kaleidoscopic design utilizing mirror-polished stainless steel is a feature of this landmark building.

The kaleidoscopic design of this landmark pays homage to the mirror glass-covered ‘central apartment’ that once stood in its place. The design intent was to reflect the colours and shades of pedestrians as a simile to the particular energy behind the fashion industry. The resulting kaleidoscopic escalator tunnel is made from various tilted mirror-polished stainless-steel panels, and act as a gateway transition into the building.
Kikukawa participated in the stainlesssteel construction of this mirrored entrance designed by the worldrenowned Hiroshi Nakamura of NAP.
The material used was 3mm thick stainless steel grade JIS G4304 SUS304 – USA (UNS) AISI304(S30400) equivalent.

Technology and quality

In implementing this kaleidoscope, several considerations and solutions were required.
The mirror-polished finish, known as one of the most unforgiving metal finishes, is the root cause of the challenge. The design concept required high-quality mirror-polished finish panels as the reflections were intended to induce the band-wagon effect of people lining up.
Another challenge was the installation. To fully implement the kaleidoscopic effect, the shapes and installation angles of each panel were different. The project demanded both expertise and comprehensive metalworking ability, from providing the design details to quality controlling during fabrication and installation.

Fibre laser welding

Mirror-polished stainless-steel panels without any distortion were key to this landmark’s design. While typical mirror-polished stainlesssteel panels are assembled to the
backing frames by stud welding the back of the panel and bolting, this detail results in stud marks appearing on the surface of the mirror-polished panels. Thus, projects requiring high quality mirror-polished stainless steel panels opt to use the 5.0mm thick stainless steel. However, the cost and weight of the 5.0mm panel were an issue for this project. Thus Kikukawa developed and tested a new detail of honeycomb backed 3.0mm thick stainless steel, a detail made possible by the high-quality welding of the fibre laser.
Conventional welding methodologies would have compromised the quality of the mirror-polished stainless steel to ensure the necessary strength of the panels. By using fibre laser welding, a technology that achieves high strength and minimal heat-induced deformation and discolouration, and carefully selecting the welding areas, Kikukawa was able to ensure the necessary strength and quality.

Uniquely-shaped kaleidoscope

Every panel in the kaleidoscope is a unique shape and is installed at a different angle.

Flexible panel system

The kaleidoscope panels cover roughly 350 m2, composed of 300 pieces of triangular mirror-polished panels each with an original shape and installed at varying angles. To precisely install these panels, Kikukawa devised and proposed a new backing frame system that would absorb possible on-site tolerances.
The tip of the panel is fixed with a cone-shaped substructure to secure the installation precision. The backing frames are fabricated by pipe cradlings to absorb any tolerances and allow the precise installation of panels with varying angles. This installation detail allows greater flexibility for on-site installation, leading to a smoother and precise implementation.
Looking down the kaleidoscopic entrance from the second-floor landing, the reflections of the street and the pedestrians are overwhelming.

About this Featured Story

This Featured Story first appeared in Stainless Steel World February 2021 magazine. To read many more articles like these on an (almost) monthly basis, subscribe to our magazine (available in print and digitally).

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All images were taken before the COVID-19 pandemic, or in compliance with social distancing.

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